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        <p>Library Version 11.2.5.3</p>
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          <th colspan="3" align="center">DB_ENV-&gt;memp_stat()</th>
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          <td width="20%" align="left"><a accesskey="p" href="mempregister.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 8. 
              The  DB_MPOOLFILE Handle
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            <h2 class="title" style="clear: both"><a id="mempstat"></a>DB_ENV-&gt;memp_stat()</h2>
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      <pre class="programlisting">#include &lt;db.h&gt;

int
DB_ENV-&gt;memp_stat(DB_ENV *env, DB_MPOOL_STAT **gsp,
    DB_MPOOL_FSTAT *(*fsp)[], u_int32_t flags);  </pre>
      <p>
         The <code class="methodname">DB_ENV-&gt;memp_stat()</code> method returns the memory pool (that is, the
         buffer cache) subsystem statistics.
    </p>
      <p>
         The <code class="methodname">DB_ENV-&gt;memp_stat()</code> method creates statistical structures of
         type <code class="literal">DB_MPOOL_STAT</code> and <code class="literal">DB_MPOOL_FSTAT</code>, and copy
         pointers to them into user-specified memory locations.  The cache statistics are stored in
         the <code class="literal">DB_MPOOL_STAT</code> structure and the per-file cache statistics are stored
         the <code class="literal">DB_MPOOL_FSTAT</code> structure.
    </p>
      <p>
         Statistical structures are stored in allocated memory.  If
         application-specific allocation routines have been declared (see
         <a class="xref" href="envset_alloc.html" title="DB_ENV-&gt;set_alloc()">DB_ENV-&gt;set_alloc()</a> 
         for more information), they are used to allocate the memory;
         otherwise, the standard C library <span class="bold"><strong>malloc</strong></span>(3) is used.  The caller is responsible
         for deallocating the memory.  To deallocate the memory, free the
         memory reference; references inside the returned memory need not be
         individually freed.
    </p>
      <p>
         If <span class="bold"><strong>gsp</strong></span> is non-NULL, the global
         statistics for the cache <span class="bold"><strong>mp</strong></span> are
         copied into the memory location to which it refers. The following
         <code class="literal">DB_MPOOL_STAT</code> fields will be filled in:
    </p>
      <div class="itemizedlist">
        <ul type="disc">
          <li>
            <p>
                          <span class="bold"><strong>u_int32_t st_gbytes;</strong></span>
                </p>
            <p>
                         Gigabytes of cache (total cache size is st_gbytes + st_bytes).
                </p>
          </li>
          <li>
            <p>
                        <span class="bold"><strong>u_int32_t st_bytes;</strong></span>
                </p>
            <p>
                        Bytes of cache (total cache size is st_gbytes + st_bytes).
                </p>
          </li>
          <li>
            <p>
                        <span class="bold"><strong>u_int32_t st_ncache;</strong></span>
                </p>
            <p>
                        Number of caches.
                </p>
          </li>
          <li>
            <p>
                        <span class="bold"><strong>u_int32_t st_max_ncache;</strong></span>
                </p>
            <p>
                        Maximum number of caches, as configured with the 
                        <a class="xref" href="envset_cache_max.html" title="DB_ENV-&gt;set_cache_max()">DB_ENV-&gt;set_cache_max()</a> 
                         method.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>roff_t st_regsize;</strong></span>
                </p>
            <p>
                        Individual cache size, in bytes.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>size_t st_mmapsize;</strong></span>
                </p>
            <p>
                        Maximum memory-mapped file size.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>int st_maxopenfd;</strong></span>
                </p>
            <p>
                        Maximum open file descriptors.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>int st_maxwrite;</strong></span>
                </p>
            <p>
                        Maximum sequential buffer writes.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>db_timeout_t st_maxwrite_sleep;</strong></span>
                </p>
            <p>
                         Microseconds to pause after writing maximum sequential buffers.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_map;</strong></span>
                </p>
            <p>
                         Requested pages mapped into the process' address space (there is no
                         available information about whether or not this request caused disk
                         I/O, although examining the application page fault rate may be
                         helpful).
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_cache_hit;</strong></span>
                </p>
            <p>
                        Requested pages found in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_cache_miss;</strong></span>
                </p>
            <p>
                        Requested pages not found in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_create;</strong></span>
                </p>
            <p>
                        Pages created in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_in;</strong></span>
                </p>
            <p>
                        Pages read into the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_out;</strong></span>
                </p>
            <p>
                        Pages written from the cache to the backing file.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_ro_evict;</strong></span>
                </p>
            <p>
                        Clean pages forced from the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_rw_evict;</strong></span>
                </p>
            <p>
                        Dirty pages forced from the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_trickle;</strong></span>
                </p>
            <p>
                        Dirty pages written using the 
                        <a class="xref" href="memptrickle.html" title="DB_ENV-&gt;memp_trickle()">DB_ENV-&gt;memp_trickle()</a> 
                         method.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_pages;</strong></span>
                </p>
            <p>
                        Pages in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_page_clean;</strong></span>
                </p>
            <p>
                        Clean pages currently in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_page_dirty;</strong></span>
                </p>
            <p>
                        Dirty pages currently in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_hash_buckets;</strong></span>
                </p>
            <p>
                        Number of hash buckets in buffer hash table.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_hash_examined;</strong></span>
                </p>
            <p>
                         Total number of hash elements traversed during hash table lookups.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_hash_longest;</strong></span>
                </p>
            <p>
                        Longest chain ever encountered in buffer hash table lookups.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_hash_mutexes;</strong></span>
                </p>
            <p>
                    The number of hash bucket mutexes in the buffer hash table.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_hash_nowait;</strong></span>
                </p>
            <p>
                         Number of times that a thread of control was able to obtain a hash
                         bucket lock without waiting.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>u_int32_t st_hash_searches;</strong></span>
                </p>
            <p>
                        Total number of buffer hash table lookups.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_hash_wait;</strong></span>
                </p>
            <p>
                         Number of times that a thread of control was forced to wait before
                         obtaining a hash bucket lock.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_hash_max_nowait;</strong></span>
                </p>
            <p>
                         The number of times a thread of control was able to obtain the hash
                         bucket lock without waiting on the bucket which had the maximum number
                         of times that a thread of control needed to wait.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_hash_max_wait;</strong></span>
                </p>
            <p>
                         Maximum number of times any hash bucket lock was waited for by a
                         thread of control.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_region_wait;</strong></span>
                </p>
            <p>
                         Number of times that a thread of control was forced to wait before
                         obtaining a cache region mutex.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_region_nowait;</strong></span>
                </p>
            <p>
                         Number of times that a thread of control was able to obtain a cache
                         region mutex without waiting.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_mvcc_frozen;</strong></span>
                </p>
            <p>
                        Number of buffers frozen.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_mvcc_thawed;</strong></span>
                </p>
            <p>
                        Number of buffers thawed.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_mvcc_freed;</strong></span>
                </p>
            <p>
                        Number of frozen buffers freed.
                </p>
          </li>
          <li>
            <p>
                        <span class="bold"><strong>uintmax_t st_alloc;</strong></span>
                </p>
            <p>
                        Number of page allocations.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_alloc_buckets;</strong></span>
                </p>
            <p>
                        Number of hash buckets checked during allocation.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_alloc_max_buckets;</strong></span>
                </p>
            <p>
                        Maximum number of hash buckets checked during an allocation.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_alloc_pages;</strong></span>
                </p>
            <p>
                        Number of pages checked during allocation.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_alloc_max_pages;</strong></span>
                </p>
            <p>
                        Maximum number of pages checked during an allocation.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_io_wait;</strong></span>
                </p>
            <p>
                        Number of operations blocked waiting for I/O to complete.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_sync_interrupted;</strong></span>
                </p>
            <p>
                        Number of mpool sync operations interrupted.
                </p>
          </li>
        </ul>
      </div>
      <p>
         If <span class="bold"><strong>fsp</strong></span> is non-NULL, a pointer to a
         NULL-terminated variable length array of statistics for individual
         files, in the cache <span class="bold"><strong>mp</strong></span>, is copied
         into the memory location to which it refers.  If no individual files
         currently exist in the cache, <span class="bold"><strong>fsp</strong></span>
         will be set to NULL.
    </p>
      <p>
         The per-file statistics are stored in structures of type <code class="literal">DB_MPOOL_FSTAT</code>.
         The following <code class="literal">DB_MPOOL_FSTAT</code> fields will be filled in for each file in
         the cache; that is, each element of the array:
    </p>
      <div class="itemizedlist">
        <ul type="disc">
          <li>
            <p>
                          <span class="bold"><strong>char * file_name;</strong></span>
                </p>
            <p>
                        The name of the file.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>size_t st_pagesize;</strong></span>
                </p>
            <p>
                        Page size in bytes.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_cache_hit;</strong></span>
                </p>
            <p>
                        Requested pages found in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_cache_miss;</strong></span>
                </p>
            <p>
                        Requested pages not found in the cache.
                </p>
          </li>
          <li>
            <p>
                        <span class="bold"><strong>u_int32_t st_map;</strong></span>
                </p>
            <p>
                        Requested pages mapped into the process' address space.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_create;</strong></span>
                </p>
            <p>
                        Pages created in the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_in;</strong></span>
                </p>
            <p>
                        Pages read into the cache.
                </p>
          </li>
          <li>
            <p>
                         <span class="bold"><strong>uintmax_t st_page_out;</strong></span>
                </p>
            <p>
                        Pages written from the cache to the backing file.
                </p>
          </li>
        </ul>
      </div>
      <p>
              The <code class="methodname">DB_ENV-&gt;memp_stat()</code> method may not be called before the 
              <a class="xref" href="envopen.html" title="DB_ENV-&gt;open()">DB_ENV-&gt;open()</a>  method is called.
    </p>
      <p>
         The <code class="methodname">DB_ENV-&gt;memp_stat()</code> <span>
            <span>
                  method returns a non-zero error value on failure and 0 on success.
            </span>
            
        </span>
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp53261848"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp53286184"></a>gsp</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>gsp</strong></span> parameter references memory
                          into which a pointer to the allocated global statistics structure is
                          copied.
                     </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp53289784"></a>fsp</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>fsp</strong></span> parameter references memory
                          into which a pointer to the allocated per-file statistics structures
                          is copied.
                     </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp53290560"></a>flags</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
                          or the following value:
                     </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p><a id="mempstat_DB_STAT_CLEAR"></a>
                  <code class="literal">DB_STAT_CLEAR</code>
            </p>
                <p>
                Reset statistics after returning their values.
            </p>
              </li>
            </ul>
          </div>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp53295480"></a>Errors</h3>
            </div>
          </div>
        </div>
        <p>
                         The <code class="methodname">DB_ENV-&gt;memp_stat()</code> <span>
            <span>
                 method may fail and return one of the following non-zero errors:
            </span>
            
        </span>
                    </p>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp53300128"></a>EINVAL</h4>
              </div>
            </div>
          </div>
          <p>
                An invalid flag value or parameter was specified.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp53298832"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
                 <a class="link" href="env.html" title="Chapter 5.  The DB_ENV Handle">DB_ENV</a>, <a class="link" href="memp.html" title="Chapter 8.  The DB_MPOOLFILE Handle">DB_MPOOLFILE</a> 
            </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp53301208"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
                     <a class="xref" href="memp.html#memplist" title="Memory Pools and Related Methods">Memory Pools and Related Methods</a> 
                </p>
      </div>
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